Angular 16 introduces Signals, and this example is to show how to unit test Signal output<T>().

.ts file

import { Component, EventEmitter, Output } from '@angular/core';

@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html'
})
export class MyComponent {
  @Output() actionTriggered = new EventEmitter<void>();

  onClick() {
    this.actionTriggered.emit();
  }
}


.html file

<button (click)="onClick()">Click me</button>

.spec file

import { ComponentFixture, TestBed } from '@angular/core/testing';
import { MyComponent } from './my-component.component';
import { By } from '@angular/platform-browser';

describe('MyComponent', () => {
  let component: MyComponent;
  let fixture: ComponentFixture<MyComponent>;

  beforeEach(() => {
    TestBed.configureTestingModule({
      declarations: [MyComponent]
    });

    fixture = TestBed.createComponent(MyComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should emit actionTriggered signal when button is clicked', () => {
    // 创建一个 spy 来监听信号的调用
    const signalSpy = jasmine.createSpy('signalSpy');

    // 订阅信号
    component.actionTriggered.subscribe(signalSpy);

    // 找到按钮并触发点击事件
    const button = fixture.debugElement.query(By.css('button'));
    button.triggerEventHandler('click', null);

    // 验证 signal 被触发
    expect(signalSpy).toHaveBeenCalledTimes(1);
  });
});